1. Field of the Invention
This invention relates to ground fault interrupter apparatus of the differential transformer type and more particularly it pertains to a ground fault detector in side-by-side position with a circuit breaker.
2. Description of the Prior Art
It is important in ground fault protection to have three essential functions basically combined into a single unit; namely, overload protection, short circuit protection, and ground fault protection. Essentially a circuit breaker provides the overload and short circuit protection, however, the ground fault protection has been, in earlier systems, provided as an add-on structure to the circuit breaker. One difficulty with the add-on structure is that it adds to the total bulk of the original circuit breaker and is therefore not usually readily adaptable to installation on the load center or a panelboard by the conventional plug-in or bolt-on method.
Associated with the foregoing is a problem of providing a unified ground fault-circuit breaker having enhanced operating capabilities, unique construction, and relatively low cost. Heretofore, circuit breakers having ground fault units added on have been too large to replace the conventional circuit breaker, such as used in the load center or panelboard of a commercial or residential building. In a miniature ground fault unit, it is necessary to completely design the electronic sensor, amplifier, and solenoid tripping means in such a way that a miniature relationship is maintained without destroying or impairing the performance of a circuit breaker. Accordingly, there is a need for a new and improved ground fault current interrupter circuit breaker unit which has a dimension corresponding to that of the conventional circuit breaker.
Moreover, it is important that the operating parts of the ground fault detector and the circuit breaker be separated from each other. One reason for that is to prevent the electronic members of the ground fault detector from becoming contaminated by debris occurring during opening and closing of the contacts of the circuit breaker, such as interruption of the arc and carbon heat, which would otherwise affect the reliability of the overall structure.